The invention relates to a process and an apparatus for purifying and concentrating charge-bearing first molecules such as proteins, nucleic acids and the like.
Molecules of biological relevance, such as nucleic acids, can be concentrated for carrying out analytical tests, for example the polymerase chain reaction (PCR), by precipitating the nucleic acids, by binding the nucleic acids to a suitable matrix, for example using an ion exchange column, and by various centrifugation methods. Specific nucleic acids can be selected from a nucleic acid mixture by concentrating and separating in a gel, by hybridizing to membranes or by complexing with specific proteins. Similar processes are used to purify proteins; also used in this instance are processes like high pressure liquid chromatography (HPLC) and antibody-dependent purification processes. Antibody-dependent processes use molecules immobilized on surfaces, such as, for example, latex beads. Known processes have the disadvantage of inadequate sensitivity and speed. In addition, they are costly to carry out.
The present invention is based on the object of providing a purification and concentration process and a corresponding apparatus with which the disadvantages of the prior art are eliminated. It is additionally intended to be possible to concentrate in particular nucleic acids, proteins and other charge-bearing molecules of predetermined degree of homology or predetermined binding affinity from a large volume.
According to the process of the invention, the object is achieved by the following steps:
a) preparation of a solution containing the first molecules,
b) contacting the solution with at least one electrode which is directly provided with a coating of second molecules having affinity for the first molecules, and
c) connecting the electrode to a means for generating an electric field to bring about a movement of the first molecules in the solution directed relative to the coating.
The electrode is expediently produced from an electrically conducting plastic. It can be a layer on an electrically nonconducting plastic support rod or a section, preferably terminal, of such a plastic support rod. It is also possible for the plastic support rod to be produced completely from electrically conducting plastic and to be provided with a handle element which is produced from an electrically nonconducting plastic and can be, for example, slipped on.
On exposure to the electric field there is utilization of the effect that the first molecules present in solution, for example nucleic acid molecules, are charge-bearing and thus able to move in the electric field. The second molecules, which due to exposure to the electric field have come into contact with or reach the direct vicinity of the coating, can bind to the first molecules thereon. Suitable binding in this case may be, in particular, ionic, covalent, hydrogen bonding or binding brought about by steric effects. No electric field may be applied while this binding is developing. The process according to the invention can be used not only when the first molecules are present in a solution. It is sufficient for the first molecules to be present in a matrix, for example gel, meat or the like, which permits migration thereof in the electric field.